There exist different approaches to determining the shape of an object. One prior approach is to use a magnetic head captive inside a gauge pin that is to be inserted into the receptacle or opening in a circuit board. One inside the openings, a group of pins serves to outline the shape or pattern being measured. Then, when a Hall effect sensor, which is mounted on the circuit board, moves along the length of the pins it determines the magnet's location and hence the pin's location.
The Hall effect technique, because it involves an expensive device for making measurements for the purpose described and requires quite exact alignment of the parts involved has serious limitations in use.
Other devices use an electrostatic sensor to detect a metal area on the gauge pin as it is translated through the circuit board. This has several advantages over the hall effect/magnetic head arrangement in that it uses a much less expensive sensor, has no critical alignment process, and simplifies the design and reduces the cost to manufacture the gauge pin. It however still requires that the electrostatic sensor be moved along the gauge pin's longitudinal axis.
Accordingly, it is desirable for a device to indicate the relative position of the gauge pin without having to move a sensor along its longitudinal axis. This would allow for a near instant indication of the gauge pin's location without all of the associated mechanical means required for the movement of the sensor.